Terminals may be divided into mobile/portable terminals and stationary terminals according to mobility. Also, glass type terminals may be classified into handheld terminals and vehicle mount terminals according to whether or not a user can directly carry.
As it becomes multifunctional, a mobile terminal can be allowed to capture still images or moving images, play music or video files, play games, receive broadcast and the like, so as to be implemented as an integrated multimedia player. Efforts are ongoing to support and increase the functionality of terminals. Such efforts include software improvements, as well as changes and improvements in the structural components.
A wearable glass type terminal which is wearable on a part of a human body is recently developed. A glass type terminal worn on a user's head may correspond to a head mounted display (HMD).
A head-mounted display (HMD) refers to various image display devices such as glasses that are worn on a user's head to allow the user to view images (contents). Various wearable computers (Wearable Computers) have been developed depending on the trend of weight reduction and size reduction of digital devices, and the HMD is also widely used.
A display unit provided in a glass type terminal such as an HMD may provide various conveniences to the user by combining with an augmented reality technology, an N-screen technology and the like beyond a simple image output function.
Recently, with the increase in the use of the HMD, methods of performing various functions according to a posture of the HMD are being actively developed. Here, the posture of the HMD is a concept including a laid state of the HMD (a worn state on the user's head), a tilted degree of the HMD, a direction that the HMD faces, a position of the HMD, a rotation of the HMD, a motion of the HMD, and the like.
To this end, it is necessary to determine (estimate, track, detect, extract, decide, identify, recognize, etc.) the posture of the HMD.
As the related art method for determining the posture of the HMD, there is a method of providing light emitting elements outside the HMD body and determining the posture of the HMD using an external camera which is a device separate from the HMD. For example, in the related art method of determining the posture of the HMD, each light emitting element is identified by synchronizing an on/off time of the light emitting element provided outside the HMD body with an opening/closing time of a shutter of the external camera, and the posture of the HMD is determined by tracking the identified light emitting element.
However, according to the related art method, since the separate external device should be used, costs increase. Further, the motion of the HMD can be detected but a moved degree of the HMD, namely, an actually moved distance or rotated degree of the HMD cannot be accurately determined.